The primary objective is to discover and develop anti-cancer drugs that target the DNA methylation process. DNA methylation changes and abnormal epigenetic gene silencing correlate perfectly with the advancement of many types of cancer. An increased DNA methyltransferase activity during the progression of many cancers leads to the loss of expression of "tumor suppressor", DNA repair and cell- cell adhesion genes. The DNA methylation process is a validated target for drug intervention, because aberrantly methylated genes can be demethylated by specific drugs that reactivate genes and restore a healthy condition. We recently discovered over 50 small molecule inhibitors of Dnmt-1, the major DNA cytosine methyltransferase, using a high throughput screen with purified enzyme. In this Phase I proposal, two methods are described that utilize a unique and innovative cell-based assay. The cells have an epigenetically silenced gene encoding the green fluorescent protein (GFP). We aim to reactivate expression by interfering with the silencing mechanism. A `secondary screen' will be done with small molecules already identified as inhibitors of Dnmt-1. A `primary screen' will broaden the search to drugs that interfere anywhere in the silencing mechanism. Drugs that prove capable of stimulating re-expression of GFP will be applied to well characterized cancer cell model systems to provide further proof of concept before entering the compounds into small animal studies. PROPOSED COMMERCIAL APPLICATIONS: DNA methylation pathway inhibitors hold great promise for the treatment and reversal of many forms of cancer. We estimate that 5 million of the 8 million non-skin cancers cases in the US involve methylation abnormalities. Because the aims of this proposal are to develop novel anti-cancer compounds, human applications will not come to fruition for a several of years after this proposal is funded.